1. Field of the Invention
The present invention relates to a sheet-medium conveying device and an image forming apparatus.
2. Description of the Related Art
In a conventional art, a sheet-medium cassette is mounted at a lower part in a main body (also referred to as an “apparatus main body”) of an image forming apparatus such as a color printer, and a sheet medium such as a sheet paper fed from the sheet-medium cassette is conveyed through a conveyance route along a plurality of image forming units. Toner images of different colors are formed on photosensitive drums of the image forming units respectively, the toner images are transferred from the photosensitive drums to the sheet medium, and then the toner images are fixed on the sheet medium by a fixing unit. As a result, a color image is formed on the sheet medium. Thereafter, the sheet medium is conveyed and then ejected from the apparatus main body onto an output stacker.
Further, in order to feed a special-purpose sheet medium such as a thin sheet paper, a thick sheet paper, a postcard and an envelope, the image forming apparatus may have a sheet-medium feed tray as a sheet-medium conveying device for feeding a sheet medium, which is provided on a side wall or another location of the apparatus main body so as to be capable of being opened from and closed to the apparatus main body. Refer to Japanese Patent Application Kokai Publication No. 2004-137078 (Patent Document 1), for example. Furthermore, in order to eject the special-purpose sheet medium, on which a color image has already been formed, the image forming apparatus may have a sheet-medium output tray as a sheet-medium conveying device for ejecting a sheet medium, which is provided on a side wall or another location of the apparatus main body so as to be capable of being opened from and closed to the apparatus main body.
In the sheet-medium feed tray and the sheet-medium output tray, a sheet-medium stacker surface on which special-purpose sheet media are to be stacked is formed by opening a main tray and unfolding an auxiliary tray by a user. However, when folding the auxiliary tray and closing the main tray, a user sometimes feels cumbersome.
To avoid such situations, there is a proposal that a main body of an image forming apparatus has a device including a main tray is opened or closed by opening or closing a sheet-medium feed tray (or a sheet-medium output tray) and an auxiliary tray which can be drawn from and inserted into the main tray. In such a sheet-medium feed tray (or a sheet-medium output tray), the auxiliary tray can be inserted into the main tray for its accommodation without moving guide members for guiding side edges of the auxiliary tray to the outside of side edges of the auxiliary tray.
However, there are problems that when a sheet medium is put on the sheet-medium stacker surface formed by a combination of the main tray and the auxiliary tray, a tip (i.e., a front end) of the sheet medium abuts against a step portion or a gap portion formed between the main tray and the auxiliary tray, thus resulting in that the sheet medium cannot be smoothly set on the sheet-medium stacker surface and that the front end of the sheet medium tends to be easily folded, buckled or damaged.